Mercury cell



Unite 2,848,407 Patented Aug. 19, 1958 MERCURY CELL Sydney Forbes, Pittsburgh, Pa., assignor to Columbia- Southern Chemical Corporation, Allegheny County, Pa., a corporation of Delaware Application October 5, 1955, Serial No. 538,747

13 Claims. (Cl. 204-219) This invention relates to an improved electrolytic cell. More particularly, the present invention relates to a means whereby the spacing maintained between the bottom face of a suspended anode and the top horizontal surface of the body of mercury on the floor of a conventional mercury cell is kept uniform automatically.

From continuous use the graphite anode surface opposite the mercury electrode in a mercury cell used for the electrolysis of alkali metal salt solution, for example, gradually erodes and, correspondingly, the inter-electrode space in the cell enlarges, thereby increasing the voltage drop across the electrodes and occasioning inefficient operation or malfunctioning of the cell.

According to the present invention, therefore, an anode assembly particularly useful for automatically compensating for the erosion of such an anode and for maintaining uniform the distance between the anode and the cathode of a flowing mercury cathode type cell conventionally employed for the electrolysis of alkali metal salt solutions has been provided. According to a particular embodiment the anode structure of the present invention comprises a block having an underface parallel with and spaced from the body of mercury on the floor of the electrolytic cell, said block having a vertically-extending rod or riser aflixed thereto which passes upwardly through and above the cover of the cell. Suspension members, such as threads or strands, the ends of which are conveniently and securely mounted on the cell cover, extend downwardly into the cell chamber and around the anode block, thereby supporting said block. The verticallyextending rod, which may be mounted on the upper surface of the anode block and extend upwardly through and above the cover, is maintained in gas-tight relationship with said cover by means of a flexible impervious seal; said sealing means should permit up and down play of said riser with respect to the cell cover and at the same time close oflf the annular space formed by the opening in the cover admitting the aforementioned riser. Electrical current is introduced into the riser by known means, as will be seen hereinafter.

The suspension members supporting the anode may be flexible tension members having very fine points of contact with the anode face thereby permitting minimum shielding of the anode from the electrolyte. Thin glass, quartz, asbestos, nylon or cellulose triacetate fiber threads, for instance, having a thread diameter of generally less than about one-eighth of an inch, preferably about onethirty-second of an inch, are particularly desirable flexible tension members. Upon erosion of the bottom face of the anode block during continuous use, said block automatically settles on the suspension members and thereby maintains a uniform inter-electrode space.

The anode structure has a horizontal face on the lower side thereof parallel to a body of mercury having a horizontal face on its upper side, the anode face being suspended above, spaced from and substantially parallel to the body of mercury. The suspension members, e. g., strands, cords, threads, wires, etc., should extend between said anode and the body of mercury in contact with the lower face of the anode, said anode resting upon and being supported by said strands. Furthermore, although the ends of the suspension members are preferably mounted on the cell cover, it is within the purview of the present invention to attach the ends of said memers to the sides of the cell, or both to the sides and to the cover.

The advantages of the present invention are readily apparent. The anode assembly disclosed herein precludes any intermittent adjustments to maintain a uniform interelectrode space; furthermore, it precludes the use of supports, for example, mounted on the floor of the cell to regulate the inter-electrode gap, thus avoiding the difliculties caused by encrustation of said supports with calcareous deposits from impure brine after continuous contact therewith. These and many other advantages will be apparent from the description to follow.

In a preferred embodiment of the present invention the suspension members are glass fiber threads which are fastened to the cover in a convenient manner and extend downwardly and around the face of the anode block, thereby supporting it. The ends of said threads may be attached to the underside of the cover by means of hingefasteners or spring clamps, or the like, for example, there eing fasteners or clamps for the respective ends of the threads. According to another embodiment of the present invention, the thread ends may be brought together and conveniently fastened by one or more clamps.

According to a still further and preferred embodiment, openings may be maintained in the cover through which the thread ends are passed and fastened exteriorly. Gastight seal means should be maintained in these openings to avoid escapage of gaseous eflluents. A convenient structure for exteriorly fastening'the glass threads and maintaining an impervious seal comprises two spaced apart, vertically extending lugs or flanges on the top surface of the cell cover, between which lugs or flanges are the openings in the cover through which the threads are made to pass. The ends of the threads are drawn up through the openings in the cover to a height at least to the top of the flanges, preferably one-half inch or more beyond the top, and a wedge, preferably made of on elastomeric material, is driven between the flanges and in looking position with the glass threads. Thus a, gastight seal is effected. Where the anode structures are arranged in series, as shown in the drawings, Figure 1, the flange in the cover of a cell at the point where said cover abuts the next adjoining cell cover may be used as one of the spaced apart flanges above-described.

The above-mentioned impervious seal at the opening in the cell cover admitting the anode riserrnay comprise a flexible sleeve, such as a wax-coated glass cloth sleeve or any suitable sleeve made of material which is inert to the reactants or the reaction products, brought down over the anode riser and fastened to a flange collar surrounding the anode riser, said collar being fastened to the cover and extending upwardly from the edge or thereabouts of the opening in said cover admitting the riser. One end of the above-mentioned sleeve may be made to extend over the said collar in a tightly-fitting relationship and the other end over the anode riser at a point below the top of said riser.

To insure a tightly-fitting relationship and to avoid displacement of the sleeve at any point a metallic collar clamp may be placed over the sleeve at the point where it envelops the cell cover collar and another collar clamp may be placed over the sleeve at a point where the sleeve directly envelops the anode riser.

The present invention will be more thoroughly understood in the light of the following detailed description taken-in conjunction with the accompanying drawrugs.

Figure 1 is a fragmentary longitudinal section of a mercury cell and representsia particular embodiment of the present invent-ion. Figure 2 is a fragmentary longitudinal section of a mercury 'cell and represents another particulanembodiment ofthepresent invention. Figures 3 and 4 are diagrammatic views of suspension membennetworks. Figures 5 and 6-are cross-sectional views in perspective of-strands employable as suspension members.

Referring now to the drawings, in Figure 1 the electrolytic cell floor-1'has a body of mercury 2 thereon. On the surface'ofsaid mercury is the electrolyte 3. Directly above the-mercuryan'd spaced therefrom is suspended anode block 4 made of graphite; a graphite riser 5 extends vertically therefrom and upwardly through a cell cover 6. 'Theopening in-said cover admitting the graphite riser is -surroundedby a flanged collar 7 to which an impervious fiexibleseal 8 is attached by means of a metallic collar clamp 9, said impervious seal also being attached to the graphite riser at a point about one-third of the'way down from the top of said riser by means of a second metallic collar clamp 10. Means 11 is provided at the top of the graphite riser for admitting current to the anode assembly from an anode lead in the conventional manner.

Suspension members 12 extend downwardly and around the anode block and are mounted in the cell cover by means of flange 13 and flange 14 which admit wedges 15 and 16 therebetween in locking relationship with suspension member 12 which extends upwardly through the cell cover and overlaps flange 14 as shown.

The inverted J-shaped flange 13 of cover 6 overlaps in locking position the adjacent vertically-extending flange of channel member 19, whereas the corresponding J-shaped cover flange 13a of cover 6a of an adjoining cell cover may overlap in locking position the opposite vertically-extending flange member of channel member 19, said J-shaped flanges 13 and 13a overlapping the vertical flanges of channel member 19 to a point along the inner-surface of said flanges. Into the space thus formed between' the flanges of channel member 19 and the downwardly'extending flanges of J-shaped flanges 13 and 13a an adhesive material 20, such as putty, may be placed to seal the covers together.

Cover connecting means are thus provided which afford gas-tight seals between cell covers in series and, in addition, afford a removable anode assembly. Cell cover 6, for instance, may be disengaged at flange 13 from channel member 19 by removing the adhesive material 20 and lifting upwardly. Thus, anode block 4 and riser 5 are easily accessible and may be removed for replacement, or for any reason whatsoever. As may be seen from the drawing, the inner surfaces of cell cover 6, for instance, are protected with an insulatory material 21; an elastomer or any material inert to the reactants or reaction products in the cell chamber may be employed. Channel member 19 is also protected with an insulatory material 22, the insulation accomplishing a dual effect, that is, the surfaces of channel member 19 exposed to the inner chamber are protected from the reactants and reaction products and the surfaces not exposed to the inner chamber provide better locking'and sealing relationship with flanges l3 and 13a as a result of the insulatory material.

Referring now to Figure 2, another particular embodiment of the anode assembly is shown wherein the suspension members 12 are affixed to the cell cover 6 and the anode block 4 in a different manner. The ends of suspension members 12 are passed upwardly to the outer surface of cell cover 6 and attached thereto by means of an adhesive material 28, such as an epoxytype or a polyurethane resin, or the like. Slots, such as saw cuts, are madeto extend vertically the full height of opposite sides of anode block 4 and admit suspension members 12 therein asshown by referencecharacter 29. Said slots prevent the suspension members from being displaced along the sides of the anode block.

Figures 3 and 4 simply show several preferred types of suspension members. Figure 3 shows threads all of which are in parallel relationship. Figure 4 shows one heavy thread 25 which fans out into numerous threads 26.

According to a further embodiment of the present invention, the opening through which thread .12 (Figure 1) passes through'cover6 may-consist of one long narrow slit extending across the cell'cover through which the ends of thread suspension members are brought and locked in position between flange 14' and wedges 15 and 16; by the -sarnetoken, however, the flange and wedges would extend across the cell at least the distance of the slit.

Another modification would be to have individual holes or openings exten'dingthrough the cell cover and arranged in series across 'thecell, each'o'f said openings admitting one or "more'threads which couldbelocked into position as just stated. Where a suspension member such as that depicted in Figure 4 is employed fewer yet larger openings'in-thecell cover-would berequired since stem 25 could be 'placedand locked therein and threads 26 could thenflare down and around the anode block 4 and support said block inhammock-fashion. Here again, by the'same'tol en,flange-14'and wedges 15 and 16 would not necessarily extend the width of'the cover but would simply be large enough to afford a gas-tight seal at the point where stem25 emerges from the cell cover.

In the interest'of providing suspension members which allow uniform 'erosionof the graphite anode the diameter of the suspension member threads should be relatively small, 'as"statedhereinabove. Although flat suspensionmembers maybe employed, more uniform erosion of the anode block-is provided using members which are round in cross'section, as in Figure 6, or hexagonal, as in Figure 5. Obviously, the least surface contact between the suspension "member and the anode block provides'for' most even and extensive erosion of the anode block. The diameter of the strands should be generally less than one-eighth .of an inch, preferably about onethirty secondofan .inch, 'as stated hereinabove. It is also within the scope of the presentinvention to substitute allor several of'the thread suspension members with platinum or silver wire having approximately the diameter justmentioned. In such a case the metal wire should be insulatedfrom the cover at its-points of attachment thereto to prevent dissipation or squandcring of the electricity fed to the cell.

The fewer strandsrequired to support the anode block and riser the better so that less of the anode block bottom face is shielded. As a rule, less than about 0.4 of one percent of the total surface area of said anode bottom face should be covered bythe suspension members running across the face.

While the present invention has been described with reference to the specific details of said embodiments, it is not-intended that such embodiments shall be regarded as limitations upon the scope of the invention, except insofar as included inthe accompanying claims.

I claim:

1. In anelectrolytic cell of the mercury cathode type having a floor'supporting a body of mercury and having a removable mver, an anode assembly comprising a graphite block having an underface parallel with, disposed above and spacedfrom the body of mercury, said block having a vertically-extendingriser aflixed thereto which passes upwardly'through the cell cover, both said block and said riser being directly supported by thread suspension-members which extend downwardly and around the anode block in supporting contact with the underface of the blockythe endsof said thread members being securely .mounted .in the cell cover to provide that the length of the members contacting the underface of the block be disposed above and in spaced relationship with the bottom of the cell.

2. In an electrolytic cell, a body of mercury in the lower portion of the cell serving as a cathode and having a horizontal upper face, a movable anode having a horizontal lower face disposed above, spaced from and substantially parallel to the upper face of said cathode, and strands extending between said anode and cathode faces in contact with the lower face of said anode, said anode resting upon and being supported by said strands, the opposite ends of said strands being supported to provide that the lengths of the strands contacting the lower face of the anode be disposed above and in spaced relationship with the bottom of the cell.

3. The electrolytic cell of claim 2 in which the lengths of the strands contacting the lower face of the anode are disposed above and in spaced relationship with the upper face of the mercury.

4. The structure of claim 2 wherein the suspension members are nonconducting glass fiber threads.

5. The structure of claim 2 wherein the suspension members are glass fiber threads having a diameter less than one-eighth of an inch.

6. The structure of claim 2 wherein the suspension members are glass fiber threads whose ends are separately mounted in the cell cover by means of an adhesive material.

7. The structure of claim 2 wherein the suspension members are glass fiber threads whose ends extend vertically through the cell cover and between two exterior flanges on the cell cover, the thread ends being locked into position by means of a wedge fitted between said flanges and engaging said thread ends between it and one of said flanges in locking relationship.

8. In an electrolytic cell of the mercury cathode type having a floor supporting a body of mercury and having a removable cover, an anode assembly comprising a graphite block having an underface parallel with, disposed above and spaced from the body of mercury, said block having a vertically-extending riser thereon which passes upwardly through the cell cover, the annular space between said riser and the opening in the cover admitting it being sealed by a flexible impervious seal permitting free up and down play to the-riser and the anode block affixed thereto with respect to said cover, both said block and said riser being directly supported by thread suspension members which extend downwardly and around the anode block in supporting contact with the underface of the block, the ends of said thread members being securely mounted in the cell cover to provide that the length of the members contacting the underface of the block be disposed above and in spaced relationship with the bottom of the cell.

9. The structure of claim 8 wherein the suspension members are nonconducting glass threads.

10. The structure of claim 8 wherein the suspension members are glass fiber threads having a diameter less than one-eighth of an inch.

11. The structure of claim 8 wherein the suspension members are glass fiber threads whose ends are separately mounted in the cell cover by means of an adhesive material.

12. The structure of claim 8 wherein the suspension members are glass threads whose ends extend upwardly through the cell cover and between two exterior flanges on the cell cover, the thread ends being locked into position by means of a wedge fitted between said flanges and engaging said thread ends between it and one of said flanges in locking relationship.

13. In an electrolytic cell, a cathode having a horizontal upper face, a movable, erodible anode having a horizontal lower face disposed above, spaced from and sub stantially parallel to the upper face of said cathode, and

non-conducting strands extending between said anode and cathode faces in contact with the lower face of said anode, said anode resting upon and being supported by said strands, the opposite ends of said strands being supported to provide that the lengths of the strands contacting the lower face of the anode be disposed above and in spaced relationship with the bottom of the cell.

References Cited in the file of this patent UNITED STATES PATENTS 564,877 Flower July 29, 1896 862,783 Allen Aug. 6, 1907 2,073,356 Torchet Mar. 9, 1937 2,627,501 Gardiner Feb. 3, 1953 2,681,887 Butler June 22, 1954 FOREIGN PATENTS 1,047,182 France July 22, 1953 

1. IN AN ELECTROLYTIC CELL OF THE MERCURY CATHODE TYPE HAVING A FLOOR SUPPORTING A BODY OF MERCURY AND HAVING A REMOVABLE COVER, AN ANODE ASSEMBLY COMPRISING A GRAPHITE BLOCK HAVING AN UNDERFACE PARALLEL WITH, DISPOSED ABOVE AND SPACED FROM THE BODY OF MERCURY, SAID BLOCK HAVING A VERTICALLY/EXTENDING RISER AFFIXED THERETO WHICH PASSES UPWARDLY THROUGH THE CELL COVER, BOTH SAID BLOCK AND SAID RISER BEING DIRECTLY SUPPORTED BY THREAD SUSPENSION MEMBERS WHICH EXTEND DOWNWARDLY AND AROUND THE ANODE BLOCK IN SUPPORTING CONTACT WITH THE UNDERFACE OF THE BLOCK, THE ENDS OF SAID THREAD MEMBERS BEING SECURELY MOUNTED IN THE CELL COVER TO PROVIDE THAT THE LENGTH OF THE MEMBERS CONTACTING THE UNDERFACE OF THE BLOCK BE DISPOSED ABOVE AND IN SPACED RELATIONSHIP WITH THE BOTTOM OF THE CELL. 